Role of lymphocyte surface determinants in lymph node homing

A carbohydrate neoepitope that is up-regulated on human mononuclear leucocytes by neuraminidase treatment or by cellular activation

The expression of cell-surface antigens can delineate specific leucocyte developmental or functional stages. For example, certain membrane glycoproteins are expressed selectively on leucocyte subsets only after activation. Leucocyte activation can also induce changes in carbohydrate epitopes expressed on surface antigens. In the present studies, we report on a novel monoclonal immunoglobulin M antibody (mAb 13.22) that recognizes a unique carbohydrate epitope expressed on human leucocyte membrane proteins. Characterization of mAb 13.22 specificity by immunoblotting showed that it recognized proteins of MW approximately 95 000 and 150 000, including both CD18 and CD11b. The mAb 13.22 epitope was removed by N-glycosidase F but not by endoglycosidase H or fucosidase, demonstrating that it is an N-linked carbohydrate antigen. Interestingly, immunoblot staining was enhanced after neuraminidase treatment, suggesting that the antibody epitope might also be partially masked by sialic acid. In resting leucocytes, the mAb 13.22 antigen was expressed strongly on neutrophils, while dull staining was present on monocytes, and no lymphocyte staining was observed. In marked contrast, treatment of leucocytes with neuraminidase resulted in exposure of a mAb 13.22 neoepitope on a subset of lymphocytes (primarily T lymphocytes and natural killer cells) as well as up-regulated staining more than 18-fold on monocytes. Activation of lymphocytes in culture with phytohaemagglutinin or concanavalin A also unmasked the mAb 13.22 neoepitope on approximately 37% of the CD45RO+ lymphocytes. Furthermore, analysis of leucocytes collected from the synovial fluid of patients with rheumatoid arthritis showed that approximately 18% of the lymphocytes present expressed the mAb 13.22 neoepitope. Taken together, our results suggest that the mAb 13.22 carbohydrate neoepitope could represent a physiologically relevant marker that is up-regulated on leucocyte subsets during the inflammatory response.

Reversible binding of sialidase-treated rat lymphocytes by homologous peritoneal macrophages

After sialidase treatment, lymphocytes disappear from the blood stream, but reappear after a few hours. The behavior of sialidase-treated rat lymphocytes was investigated by in vitro binding studies with homologous peritoneal macrophages. A lymphocyte mixture from thymus and spleen was treated with sialidase and cultured up to 55 h, and at various times, the binding of the lymphocytes to glass-adherent macrophages was studied by light and electron microscopy; vital lymphocytes were only bound but not phagocytosed, and the interaction with macrophages was inhibited by D-galactose. During culture of lymphocytes, either separately or with macrophages, the binding was more and more reduced, and a second sialidase treatment of cultured lymphocytes led again to increased binding which could be inhibited by D-galactose. This change did not occur in the presence of N-acetyl-2,3-didehydro-2-deoxyneuraminic acid, an inhibitor of sialidases, showing the sialic acid specificity of this phenomenon. Thus, the reversibility of lymphocyte binding could be explained by resynthesis of cell surface sialic acids.

The immunosuppressive effects of bilirubin

The strong effects of bilirubin on various levels of the immune system are multifactorial. Concerning the mechanisms of these effects, we hypothesize that the primary causes of the described actions of bilirubin are the direct interaction of bilirubin molecules with cell membranes.

Lymphocyte homing

The phenomenon of "homing" is discussed with respect to patterns of lymphocyte circulation and the molecules on the surface of both endothelium and lymphocytes that mediate this process. In addition, the data are analysed in the context of a model for lymphocyte homing.

Dissemination pattern of two immunologically induced transplanted malignant lymphomas in C57 B1/6J mice

The need for syngenic tumors to elucidate factors in lymphoma dissemination prompted us to induce new lymphomas in a series of inbred C57B1/6J mice. The method of induction, immunosuppression and simultaneous immunostimulation, had a high mortality rate, but gave us 2 transplantable lymphomas. These tumors are described and compared in the present paper, with emphasis on their dissemination patterns. Both tumors disseminated rapidly from tail transplants to lymphoid organs, lungs and liver. They were characteristically dissimilar, however, in their s.c., i.p. and i.v. transplantabilities.

Synergistic effect of N-acetyl-D-glucosamine (NAG) on mitogenic, antigenic and allogeneic stimulation of normal human lymphocytes

The effect of N-acetyl-D-glucosamine (NAG) on in vitro stimulated human peripheral blood lymphocytes was investigated. NAG was added to lymphocyte cultures stimulated by the mitogen PHA, the antigen PPD or to one-way-stimulated mixed lymphocyte cultures from unrelated donors. The results indicate that NAG (1-2 micrograms/ml) in appropriate experimental conditions has an enhancing effect on DNA and protein synthesis induced by PHA, PPD and allogeneic cells. Addition of NAG (1-2 micrograms/ml) to unstimulated lymphocyte cultures had no effect on DNA or protein synthesis.

Effect of enzymic removal of cell surface constituents on metastatic colonisation potential of mouse mammary tumour cells

Trypsin treatment of viable cells from 24 spontaneous murine mammary carcinomas resulted in a mild but reproducible diminution in their capability to colonise the lung after i.v. reinoculation but did not alter the distribution of deposits formed. The effects were similar on tumours of high and of low colonisation potentials. Neuraminidase and hyaluronidase did not exert any effect on metastatic colonisation potential, although all 3 enzymes were shown to be active and specific in cleaving their purified substrates, under the conditions in which they were used on the cells. Trypsin and neuraminidase were also shown to release characteristic components from the surfaces of living tumour cells, although hyaluronidase did not release detectable quantities of N-acetyl glucosamine indicating that there is little hyaluronic acid-related mucopolysaccharide on the surface of these mammary tumour cells. The results provide direct evidence suggesting that surface protein composition exerts an effect on the metastatic colonisation capability of mammary tumour cells.

Role of the H-2 complex in the homing affinity of injected lymphoid cells to the host's lymph nodes

The role of H-2 and non-H-2 gene products was studied in a model of non-immune cell-cell interactions which underlie the homing affinity to lymph nodes of injected 51Cr-labelled lymph node cells. The effect of various donor-recipient combinations was tested by comparing the allogeneic/syngeneic ratio of radioactivity recovered from the lymph nodes. The homing affinity was reduced to about 50% when the donor-recipient incompatibility extended over the whole H-2 chromosome. When confined to a single region (H-2K, I or D) H-2 incompatibility caused no significant allogeneic inhibition of the homing affinity. The cumulative effect of two partial incompatibilities (K + I or D + I) was, however, reflected in a significant allogeneic inhibition. Non-H-2 incompatibilities had, as a rule, a weak effect; the non-H-2 gene products may not be directly involved in the cell interactions under test.

Control mechanism of lymphocyte traffic. Altered migration of 51Cr-labeled mouse lymph node cells pretreated in vitro with phospholipases

Glycoproteins have so far been the only surface components thought to be of importance in the process of recognition between circulating lymphocytes and endothelial cells of the lymph node post-capillary venules and thus in the control of lymphocyte traffic. In this paper the effect of in vitro treatment of 51Cr-labeled mouse lymph node cells with phospholipases (PL) (A and C) on their migration into syngeneic recipients was investigated. PL-A and PL-C treated cells migrated differently from control (untreated) cells. Diminished numbers of PL-A-treated lymphocytes were found in the lymph nodes at 1, 6 and 24 h after cell transfer with a simultaneous increase in the lungs at 1 h, and spleen at 6 h after transfer. PL-C-treated cells remained in the blood longer than untreated cells. We conclude that factors other than the integrity of surface glycoproteins are involved in the control of lymphocyte traffic. The roles played by cell adhesion, in particular cell-to-cell interactions in regulating the rate of cell migration, are discussed.

The hematopoietic microenvironment of the bone marrow: an ultrastructural study of the stroma in rats

The bone marrow contains branching vascular sinuses lying in a fibroblastic stroma which supports hematopoiesis. This paper describes the stroma and vascular sinuses by scanning and transmission electron microscopy and in freeze-fracture etch replicas in normal fat femoral marrow and in rats made eosinophilic by larvae of trichinella spiralis. The stroma consists primarily of reticular cells which ensheath sinuses as adventitial cells and branch into the surrounding hematopoietic space. They form a spongework on which hematopoietic cells are arranged. Erythroblasts, clustered into islets, and megakaryocytes lie just outside sinuses. Granulocytes, until the metamyelocyte stage, lie in the midst of the hematopoietic cords. Lymphocytes, monocytes and likely stem cells, are clustered about arterial vessels. Macrophages occur throughout the marrow. Fat cells occur adventitial to vascular sinuses and appear to be reticular cells which accumulate fat. Processes of reticular cells closely envelope hematopoietic cells or protrude into them. Reticular cells contain rough ER and are likely fibroblastic. The argyrophilic reticular fibers of the marrow are, however, slender and scanty. Reticular cells are rich in filaments and they may contain many microtubules. They are not phagocytic and possess few lysosomes. The reticular cell cover of a vascular sinus is lifted away as maturing hematopoietic cells approach the sinus, preparatory to crossing the endothelium and entering the circulation. Maturing granulocytes often show microvilli on reaching the basal endothelial surface. The level of eosinophils in the marrow may increase from approximately four to more than 20% after injection of trichinella larvae. Close distinctive association of reticular cells and eosinophils are marked. Reticular cells provide a physical spongwork on which hematopoietic cells are supported. But I postulate that they also trap and induce differentiation of hematopoietic stem cells, and sort the differentiating hematopoietic cells into characteristic locations in their spongework.

Immunological properties of murine thymus-dependent lymphocyte surface glycoproteins

The immunological properties of two murine thymus-dependent (T) lymphocyte surface glycoproteins, T200 and T25, were investigated. T200 is a lymphocyte-specific antigen with a high degree of species specificity. It shares antigenic determinants with molecules present on thymus-independent (B) lymphocytes. T25 has antigenic determinants which cross-react with antigens on mouse brain, rat thymocytes and rat brain. An antiserum against a purified rat brain glycoprotein which carries Thy-1.1 reacts with T25. Absorption of this antiserum with BALB/c thymocytes or brain homogenate produces a Thy-1.1 specific serum which reacts with T25 from AKR/J thymocytes but not with T25 from AKR/Cum thymocytes. These results confirm that T25 is the molecule on the surface of mouse T cells which carries the Thy-1 antigen. T25 also carries antigenic determinants, recognized by anti-thymocyte serum (ATS), which were found on secondary mouse embryo fibroblasts and untransformed fibroblast cell lines but which were not detected on fibroblast cell lines transformed with murine sarcoma virus (MSV) or with Simian virus 40 (SV40).

Control mechanism of lymphocyte traffic. Altered distribution of 51Cr-labeled mouse lymph node cells pretreated in vitro with lipopolysaccharide

The effect of in vitro treatment of mouse lymph node cell populations with lipopolysaccharide (LPS) on their migration in syngeneic recipients was studied. LPS-exposed cells had a decreased lymph node localization and an increased spleen distribution when compared to control untreated cells, after intravenous injection into syngeneic recipients. This effect of LPS on cell traffic was maximal at 24 h and could not be detected at either 1 or 72 h after cell transfer. These changes induced on cell distribution by LPS treatment are interpreted as the consequence of a modified interaction between the circulating lymphocytes and the resident cells within the spleen of the recipients.

Surface structures influencing the migration in vivo ecotaxis of murine thymocytes, T- and B-cells

The effect of protease and neuraminidase treatment on the ecotaxis of radioactively labelled thymocytes, T- and B-cells was studied by scintillation counting and autoradiography. Each enzyme had a similar effect on all cell types. Both protease and neuraminidase treatment strongly reduced the migration to the lymph nodes while the distribution to the spleen was more profoundly reduced by neuraminidase than by protease. In contrast, a similar and less pronounced effect of the enzymatic treatments on the circulation to the Peyers patches was found. The possible structure of the surface "receptors" involved is discussed in view of the known effects of these enzymes on the cell membranes.

Cell surface receptors and lymphocyte migration

Lymphocyte subpopulations show a marked specificity in their distribution in various parts of the lymphoid system. It has been suggested that specific localization of lymphocytes depends on the presence of homing" receptors on their cell surface. The present paper summarizes some of the approaches used in the study of cell surface receptors involved in the migration and localization of lymphocytes. The effect of exposure of lymphocytes to antibodies, enzymes or lectins, on their capacity for localization is described. It is concluded that the experimental procedures employed do not provide conclusive evidence as to the mechanisms of lymphocyte localization, and that the role of homing receptors is still far from clear.